1. Technical Field
The present invention relates to a liquid ejecting head which ejects liquid from nozzle orifices, a liquid ejecting head unit, and a liquid ejecting apparatus and, in particular, to an ink jet type recording head which discharges ink as liquid, an ink jet type recording head unit, and an ink jet type recording apparatus.
2. Related Art
As a representative example of a liquid ejecting head, for example, an ink jet type recording head is known which discharges ink droplets from nozzle orifices by using pressure occurring by displacement of piezoelectric elements. In the ink jet type recording head, a portion of a pressure generation chamber communicating with the nozzle orifice is constituted by a vibration plate and an ink droplet is discharged from the nozzle orifice by providing pressure to ink supplied to the pressure generation chamber, by deformation of the vibration plate by the piezoelectric element.
Also, with respect to such an ink jet type recording head, there is proposed an ink jet type recording head in which a piezoelectric element is fixed at one end portion thereof to a vibration plate and at the other end portion to a fixed plate, the fixed plate is fixed to a case, thereby holding the piezoelectric element, and an ink droplet is discharged by generating a pressure change in a pressure generation chamber by deforming the vibration plate by extension and contraction in the axial direction of the piezoelectric element.
In such an ink jet type recording head, since the case is formed by molding of a resin material, there is a problem such that rigidity is low, so that a repulsive force when driving the piezoelectric elements cannot be suppressed. In particular, in a case where the piezoelectric elements are fixed to a housing portion penetrating the case, since at both end portions in a juxtaposition direction of the piezoelectric elements of the case, rigidity is high due to wall surfaces of the housing portion and at the central portion in the juxtaposition direction thereof, rigidity is low, the repulsive force due to driving of the piezoelectric elements cannot be uniformly suppressed, so that the recording head cannot be driven with uniform ink discharge characteristics.
For this reason, there is proposed an ink jet type recording head in which a reinforcing plate made of metal is buried in a case made of a resin material over a juxtaposition direction of piezoelectric elements, whereby the case is reinforced by the reinforcing plate (refer to JP-A-2001-293862 and JP-A-2001-71486, for example).
In this manner, in a case where the reinforcing plate is buried in the case, the reinforcing plate must be positioned at a predetermined position of a mold which molds the case. For this reason, since the case is molded while a portion of the reinforcing plate is held for positioning, the reinforcing plate is provided in a state where the portion of the reinforcing plate is exposed from the case. Such exposed portions of the reinforcing plate exposed from the case are provided at four sides of the periphery of a plate-like member having a rectangular shape. However, since it is not preferable that the exposed portions be present at the adhesion surface side of the case to the flow path unit, the exposed portions are provided at two corner portions on the discharge face side of the side faces and one side on the opposite side to the discharge face.
However, since the two corner portions on the discharge face side are close to the discharge face, some ink discharged from the nozzle orifice adheres to the discharge face and the ink adhered to the discharge face creeps up to the corner portions. The ink which has crept to the corner portions in this manner reaches the exposed portion on the opposite side to the discharge face through an interface between the molded resin of the case and the reinforcing plate and then penetrates from the exposed portion on the opposite side to the discharge face into the housing portion in the case, in which the actuator unit is housed, consequently there is a problem in that the actuator unit is damaged by the penetrated ink.
In addition, such a problem is also similarly present in a liquid ejecting head, which ejects liquid other than ink, as well as the ink jet type recording head.